Ps 98:2

“"The Lord is great in Sion, and high above all people" (ver. 2). ...He whom I spoke to thee of as above the Cherubims, is great in Sion. Ask thou now, what is Sion? We know Sion to be the city of God. The city of Jerusalem is called Sion; and is so called according to a certain interpretation, for that Sion signifieth watching, that is, sight and contemplation; for to watch is to look forward to, or gaze upon, or strain the eyes to see. Now every soul is a Sion, if it trieth to see that light which is to be seen. For if it shall have gazed upon a light of its own, it is darkened; if upon His, it is enlightened. But, now that it is clear that Sion is the city of God; what is the city of God, but the Holy Church? For men who love one another, and who love their God who dwelleth in them, constitute a city unto God. Because a city is held together by some law; their very law is Love; and that very Love is God: for openly it is written, "God is Love." He therefore who is full of Love, is full of God; and many, full of love, constitute a city full of God. That city of God is called Sion; the Church therefore is Sion. In it God is great....”